It is known to provide a threaded bolt with measurement planes. Typically, the measurement planes are formed either at a recess or an elevation with respect to the actual end planes of both the head end and the insertion end. The measurement planes are often formed by means of cold deformation and finishing. One such threaded bolt is described in European patent application 0.459.365 which issued May 28, 1991, the contents of which are incorporated herein by reference.
Another threaded bolt is known from U.S. Pat. No. 4,846,001 which issued Jul. 11, 1989, in which the threaded bolt is shown as having a head which has been provided with a recess including a measurement plane. The measurement plane has been made sufficiently smooth/level by finishing, in order to be used in ultrasonic measuring. The recess is used for accommodating a piezo-electric sensor. In another embodiment the recess is absent and the sensor is placed on top of the end plane at the head.
Frequently, existing threaded bolts exhibit several radial planes at one or both ends, situated at various axial distances measured along the center line of the threaded bolt, which can adversely affect the ability to achieve accurate measurement results.